This invention relates to a battery (also known as an accumulator), particularly but not exclusively of the lead acid type.
One known lead acid battery comprises a plurality of rectangular plates arranged parallel to one another and separated by insulating separating sheets. Alternate plates are positive and negative electrodes respectively, all the positive electrodes being connected together electrically by a first connector and all the negative electrodes being connected together electrically by a second connector, the two connectors being connected to positive and negative terminals respectively.
If the plates, all rectangular, are relatively long and narrow, and the connector and/or terminal is connected to a narrow edge, then there is a relatively long conducting path for the current from the area of the plate adjacent the opposite narrow edge to the connector or terminal. Since the conductivity of lead is significantly less than that of a metal such as copper or aluminium, there is a limit to the current carrying capacity of each electrode, since increasing the current increases the heat generated within the plates. Thus, particularly where other factors dictate that a battery has electrodes which are long and narrow, and the terminals or connectors are attached to a narrow edge of the electrodes, and further if the battery is located in a confined space, the limit on the current carrying capacity is a considerable disadvantage.
EP-A-0442599 discloses a battery having a plurality of alternating positive and negative plates; at least one tab protruding from one edge of each of the positive and negative plates; at least one tab protruding from an opposite edge of each of the positive and negative plates; a pair of negative plate straps connecting together each tab protruding from each negative plate; a pair of positive plate straps connecting together each tab protruding from each positive plate; a first diagonal bar connecting together the pair of negative plate straps; and a second diagonal bar connecting together the pair of positive plate straps.
It is an object of the present invention to provide a battery having an improved current carrying capacity.
In accordance with the invention a battery comprises a housing containing a plurality of positive plates connected in parallel and a plurality of negative plates connected in parallel, the positive plates each being of substantially the same size and rectangular shape having two long edges and a first short edge and a second short edge, and the housing also containing a member having a first end and a second end, the first end being electrically connected to the first short edges of the positive plates adjacent one of the two sets of long edges and the second end being electrically connected to the second short edges of the positive plates adjacent the same set of long edges or to the same set of long edges of the positive plates immediately adjacent to the second short edges, the members extending parallel to the long edges for most of its length and consisting of a material which has a greater conductivity than the material of the positive plates.
The negative plates may each be substantially the same size and rectangular shape having two long edges and a first short edge and a second short edge, and a further member may be provided, the further member having a first end and a second end, the first end being electrically connected to the first short edges of the negative plates and the second end being electrically connected to the second short edges of the negative plates or to one of the long edges of the negative plates immediately adjacent to the second short edges, the further member consisting of a material which has a greater conductivity than the material of the negative plates.
The negative plates and the positive plates may all be substantially the same size and rectangular shape.
The first short edges of the positive plates may be connected by a first connector which is electrically connected to a positive terminal of the battery.
The second short edges of the positive plates may be connected by a further connector which is either of the same general material as the positive plates, e.g. in the case of a lead acid battery the material is lead, or, alternatively, of the same general material as the member.
If the battery is a lead acid battery, the member preferably comprises copper, or a copper alloy such as brass, or aluminium or an alloy thereof, covered in a lead sheath. The sheath may be covered in an acid resistant material such as an epoxy resin.